1. Field of the invention
This invention relates to fluid compressors and particularly to fluid compressors having a plurality of piston and cylinder compression stages. These compressors have many practical uses in a variety of fields including that of compressing oxygen or oxygen-enriched air to serve as a breathing gas.
2. Description of the Prior Art
A compressor for this purpose is disclosed in GB-A-2177460 and utilises hydraulic fluid under pressure as the source of energy. However a potential problem with this compressor is the incompatibility of the two fluids in that should the hydraulic fluid come into contact with oxygen or highly oxygen-enriched air under pressure there is a risk of explosion. In addition the contamination of the oxygen or oxygen-enriched air by hydraulic fluid can render it unfit for use as a breathing gas and/or interfere with the operation of demand valves and other equipment concerned in regulating the delivery of the gas downstream from the compressor.
Furthermore, this compressor utilises a port plate driven by a positive displacement pressure fluid motor such as a gerotor actuated by the hydraulic fluid, and such an arrangement tends to be bulky and, consequently heavy.
There is therefore a need for a compressor which eliminates the risks associated with the use of incompatible fluids and which is more compact and lighter than the compressor of GB-A-2177460. An objective of the present invention is to provide a compressor meeting these requirements.